Carburetor vent system



July 14, 1959 J. T. WENTWORTH CARBURETOR VENT SYSTEM Filed March 26,1958 "Fuel, TANK United St t at Q GAERBURETOR VENT SYSTEM Joseph T.Wentworth,. Royal Oak, Mich., assignor to General Motors Corporation,Detroit, Mich., a corporation of Delaware Application March 26, 1958,Serial No. 724,092

8 Claims. (Cl. 261-72) which otherwise might force fuel through the fuelnozzle into the induction passage of the carburetor causing the same toflood and making starting difllcult.

To overcome this problem carburetors frequently have both internal andexternal venting devices. With an internal vent and the vehicle running,float bowl fuel vapors are vented into the carburetor induction passageand thus consumed by the engine. When the vehicle is parked or idling,on the other hand, it is common to externally vent the fuel vapors. Theexternal venting of fuel vapors frequently results in the vehiclecompartment being permeated by fuel vapor odors to the discomfiture ofthe passengers.

The present invention provides a closed or completely internally ventedcarburetor whereby the fuel vapors are returned to the vehicle gas tankwhere they are either condensed and become part of the liquid supply ofgasoline or pass to a venting passage leading to the carburetorinduction passage.

A first advantage of the present system is the elimination of obnoxiousfuel vapor odors. Secondly, the loss of externally vented fuel vapors isavoided since all vapors are either returned to the fuel tank in liquidform or pass in vapor form into the carburetor and in either event areultimately utilized by the engine.

Other objects and advantages of the present invention will be apparentfrom a perusal of the detailed description which follows.

In the drawings:

Figure 1 illustrates the subject venting system as incorporated on anautomobile; and

Figure 2 is an enlarged detail view of the venting system.

Referring to the drawings, a schematic representation of a carburetor isshown generally at 10 and includes an induction passage 12 having chokeand throttle valves 14 and 16 respectively pivotally mountedtherewithin. A carburetor float bowl is indicated generally at 18. Afuel tank 20 includes a filler pipe 22 closed by a cap 24.

In general, the fuel tank is located at the rear of a vehicle and belowthe level of the carburetor although this relationship is not critical.Fuel is normally supplied from tank 20 to the carburetor fuel bowl 18through a conduit 26 by a conventional fuel transfer pump 28. Thequantity of fuel admitted to fuel bowl 18 is controlled by aconventional float controlled valve mechanism only the float 30 of whichis shown.

Due to its inevitable proxirrrity to the engine, the fuel in the floatbowl 18 is subjected to considerable heat. The result is, of course,that particularly the lighter ends of the fuel are vaporized and thevapors collect the float bowl above the fuel level. The

2,894,736 Patented July 14, 1959 vapors must be vented to reduce thepropensity for vapor lock and also to prevent the vapor pressure fromforcing fuel through the fuel nozzle particularly during hot soakconditions.

It has been the normal practice to provide means whereby these vaporsare vented to the carburetor induction passage and consumed by theengine in the course of normal operation. However, it is found that whenthe engine is idling or even sitting under hot amb-ient conditions, theengine is unable to consume such vapors with the result that there is atendency of the fuel pressure to build up within the fuel reservoir andforce the liquid fuel through the fuel nozzles: and through theinduction passage causing flooding of the engine. As already noted, ithas been the practice to provide means for externally venting thesevapors when the throttle 16-is closed. For such an external ventingmechanism see Patent 2,771,282 Olson et al.

The effect of internal vents on hot weather idling has not been givenenough attention in the past. In hot weather, city driving, bowltemperatures as high as 20 to 40 above ambient operating temperaturesarecommon. In other words, it is possible with ambient temperatures between70 and F. to have bowl temperatures in the vicinity of to It is apparentthat at such temperatures considerable fuel vaporization will take placewith current type fuels. At idle, of course, the fuel consumption rateis at its lowest point and, in an internally vented system, the bowlvapor is most likely to be an appreciable portion of the metered fuelresulting in a rich air-fuel ratio. Consequently, good hot weatheridling cannot be obtained, particularly on present siunrner fuel blends,if all the vapor from the carburetor bowl is fed to the engine.

I As the result of tests it has been found that a normal internallyvented engine under hot weather idle conditions may increase its idlefuel flow rate by approximately 15%. Most of this 15% increase isattributable to internally vented vapor. The aforenoted fuel flow rateincrease results in extremely rough idling operation due to'overenrichment. With the subject venting system the increase in fuelflow rate under similar hot idling conditions was negligible resultingin good hot idling engine operation.

In the present device a suitable boss 32 is. formed on the float bowlcover 34 and communicates through a conduit 36 with the fuel tank fillerpipe 22. Since pipe 22 is relatively cool fuel vapor from bowl 18 andconduit 36 will condense and return to tank 20 in liquid form.

An additional conduit 38 communicates the filler pipe 22 with a venttube 40 disposed within induction passage 12 posteriorly of choke valve14. In this way provision is made for the lighter fuel vapors, which donot condense, to pass to the carburetor induction passage where theywill be ultimately consumed by the engine or else pass off in relativelysmall quantities. Since vapors remaining in the filler pipe will collectnear the upper end thereof, it is preferable to dispose the conduit 38nearer the upper end of filler tube 22 than is conduit 36.

An [important feature of the present invention is that the conduits 36and 38 are disposed, in relation to fuel tank 20 and carburetor 10, soas to prevent pockets of fuel collecting therewithin which mightotherwise create back pressures rendering the venting systemineffective. To this end, it Will be noted that the conduits 36 and 38have been disposed above either or both the fuel tank and the carburetorin such a way that any liquid fuel which might condense in the conduitswill run down- Wardly either to the fuel tank or to the carburetor butcannot collect in the conduits in any quantity suflicient to inhibit theventing function.

As a practical matter, the most likely disposition of the conduits 36and 38 would be to have them pass from under the vehicle hood upwardlythrough the body front corner posts 42 along the vehicle roof 44 andthen down- Wardly through the rear corner posts 46 to the fuel tankfiller pipe. In this way no portion of the conduits would be disposedbelow both the fuel tank and the carburetor and accordingly the conduitswould be free of liquid fuel in any detrimental quantities.

I claim:

1. A charge forming device for an internal combustion engine comprisingan air induction passage, a fuel bowl associated with said inductionpassage, a fuel tank for supplying fuel to said fuel bowl, said fueltank including a filler pipe extending therefrom, a first conduitcommunicating said fuel bowl above the fuel level with said filler pipe,and a second conduit communicating said filler pipe with said inductionpassage.

2. A charge forming device for an internal combustion engine comprisingan air induction passage, a fuel bowl associated with said inductionpassage, 21 fuel tank for supplying fuel to said fuel bowl, said fueltank including a filler pipe extending therefrom, a first conduitcommunicating said fuel bowl above the fuel level with said filler pipe,and a second conduit communicating said filler pipe with said inductionpassage, said second conduit connected to said filler pipe above theconnection thereto of said first conduit.

3. A charge foirning device as set forth in claim 2 in which all pointson said conduits are disposed above either said fuel tank or said fuelbowl.

4. A charge forming device for an internal combustion engine comprisingan air induction passage, a fuel bowl associated with said inductionpassage, a fuel tank for supplying fuel to said fuel bowl, said fueltank including a filler pipe extending therefrom, a first conduitcommunicating said fuel bowl above the fuel level with said filler pipe,and a second conduit communicating said filler pipe with said inductionpassage, all points on said 41 conduits being disposed vertically aboveeither said fuel tank or said fuel bowl.

5. A fuel venting system for a vehicle employing an internal combustionengine comprising, a charge forming device disposed near one end of saidvehicle, said device including an air induction passage, and a fuel bowlassociated with said passage and adapted to supply fuel thereto, a fueltank disposed near the other end of said vehicle, pump means forsupplying fuel from said tank to said bowl, said tank including a fillerpipe extending therefrom, a first conduit communicating said fuel bowlabove the fuel level with said filler pipe, and a second conduitcommunicating said filler pipe with said induction passage, saidconduits being disposed within the vehicle so that all points of saidconduits are disposed above either said fuel tank or said fuel bowl.

6. A fuel venting system as set forth in claim 5 in which said secondconduit is connected to said filler pipe above the connection thereto ofsaid first conduit.

7. A fuel venting system as set forth in claim 5 in which at least aportion of said conduits is supported within the roof of the vehiclebody.

8. A fuel venting system for a vehicle utilizing an internal combustionengine comprising a charge forming device comprising an air inductionpassage, a fuel bowl associated with said induction passage, a fueltank, pump means for supplying fuel from said tank to said fuel bowl,said fuel tank including a filler pipe extending therefrom, a firstconduit communicating said fuel bowl above the fuel level With saidfiller pipe, and a second conduit communicating said filler pipe withsaid induction passage.

Menneson Nov. 30, 1948 Russell Nov. 14, 1950

